Low incidence of factor VIII inhibitors in previously untreated patients with severe haemophilia A treated with octanate®: Final report from a prospective study

Introduction

Octanate^® is a human, plasma‐derived, von Willebrand factor‐stabilized coagulation factor VIII (FVIII) concentrate with demonstrated haemostatic efficacy in previously treated patients with haemophilia A.

Aim

This prospective, open‐label study aimed to assess the immunogenicity of octanate^® in previously untreated patients (PUPs).

Methods

The study monitored development of FVIII inhibitors in 51 PUPs. Tolerability, viral safety, FVIII recovery and efficacy of octanate^® for the prevention and treatment of bleeds and in surgical procedures were also assessed.

Results

Five (9.8%) of the 51 patients developed inhibitors during the study, 4 of which (7.8%) were high titre. Three inhibitor cases (5.9%) were considered clinically relevant; 2 were transient inhibitors that disappeared during regular octanate^® treatment without a change in dose or treatment frequency. Amongst 45 patients with FVIII:C <1% at baseline and who received ≥20 exposure days (EDs) or had <20 EDs but developed an inhibitor, inhibitor incidence was 11.1% (6.7% clinically relevant). All clinically relevant inhibitors developed within 20 EDs of on‐demand treatment. No inhibitors developed in PUPs receiving prophylaxis. All patients who developed inhibitors had either intron 22 inversions or large deletions. Irrespective of the reason for administration, haemostatic efficacy was rated as “excellent” in 99.6% of all infusions (4700 of 4717 infusions), and no complications were reported in 23 surgical procedures. Mean incremental in vivo recovery was 2.0%/IU/kg (±0.7) and 1.9%/IU/kg (±0.5) for the first and second assessments, respectively. Tolerability was rated “very good” in 99.9% of infusions.

Conclusion

In PUPs with severe haemophilia A, octanate^® demonstrated haemostatic efficacy with a low rate of inhibitor development.     

FEIBA in the treatment of acquired haemophilia A: Results from the prospective multicentre French ‘FEIBA dans l'hémophilie A acquise’ (FEIBHAC) registry

Factor VIII inhibitor bypass activity (FEIBA) is a recommended first‐line bypassing agent for bleeding episodes in patients with acquired haemophilia A (AHA). Due to the low incidence of AHA, available clinical data on FEIBA treatment are limited. The study aim was to delineate practice patterns in FEIBA treatment of AHA patients, the haemostatic efficacy of FEIBA, including criteria for its assessment, and safety. A prospective registry was established of AHA patients receiving FEIBA for bleeding episodes or prophylaxis at the time of invasive procedures. Data were collected at 16 participating centres in France. Patients were followed up for 3 months. Haemostatic efficacy, FEIBA regimen and FEIBA‐related adverse events were documented. Thirty‐four patients averaging 81.8 years old with standard deviation (SD) 8.1 years were included in the study: 33 for acute bleeding and one for haematoma evacuation. The mean initial dose of FEIBA for acute bleeding was 75.4 U kg^?1 (SD, 7.7 U kg^?1), most often administered twice daily, and the median duration of FEIBA treatment was 4.0 days (interquartile range, 2.2–8.0 days). FEIBA was effective in managing 88.0% of bleeding episodes (95% confidence interval, 75.8–94.5%). No baseline variables influencing treatment response could be identified. The sensitivity and specificity of an objective haemostatic efficacy scale in predicting sequential investigator assessments of haemostatic efficacy were 45.3% and 84.1% respectively. Four patients experienced a total of six serious adverse events possibly related to FEIBA. In the first prospective study specifically focused on FEIBA treatment of patients with AHA, 88.0% of bleeding episodes were effectively managed.     

Real‐life evidence in evaluating effectiveness of treatment in Haemophilia A with a recombinant FVIII concentrate: A non‐interventional study in emerging countries

Some progress has been made regarding availability of recombinant factor VIII concentrates and prophylaxis for haemophilia A in emerging countries, where plasma‐derived concentrates were used in the vast majority. Clinical studies to document their introduction and effectiveness are so far not widely available in literature. This non‐interventional study evaluates the real‐life effectiveness and safety of prophylactic and on‐demand treatment with recombinant factor VIII formulated with sucrose (rFVIII‐FS) for bleed control and preservation of joints in emerging countries from Eastern Europe, North Africa and Middle East area. One hundred and eighty‐six patients from 11 countries were enrolled, mean ± SD age 12.8 ± 12.7 years. At enrolment, majority (79.6%) had severe haemophilia A (<2% IU mL^?1), 47.8% had a target joint, 15% had an inhibitor history and one patient was on immune tolerance induction. During the 24‐month observation period, 58.1% of the patients were prescribed prophylaxis at every visit, 31.7% were on an on‐demand regimen. Patients with severe haemophilia A on prophylaxis (n = 82) had a mean annual rate of treated bleeds of 2.8 ± 4.4, whereas it was 19.1 ± 32.0 for the on‐demand group (n = 31), and a mean total Gilbert Score of 9.9 ± 10.3 at baseline and 4.1 ± 6.7 at study end; vs. 15.2 ± 17.3 and 13.7 ± 17.1 for on‐demand respectively. The majority of the bleeds (91.1%) were treated with one or two infusions. Four patients without inhibitor history had a first positive inhibitor test during the study. This study demonstrates the effective use of rFVIII‐FS in emerging countries and adds to the established safety profile of rFVIII‐FS.     

The incidence of factor VIII inhibitors in severe haemophilia A following a major switch from full‐length to B‐domain‐deleted factor VIII: a prospective cohort comparison

Although it has been suggested that switching of factor VIII (FVIII) products may increase inhibitor formation this is disputed. Half of UK patients changed rFVIII brands because of national contracting in 2010, presenting an opportunity to compare inhibitor incidence of switchers with non‐switchers. Centres were requested to test all the patients for inhibitors prior to the switching date and 6‐monthly thereafter. Positive and negative inhibitor test data were also collected to analyse for testing bias. A total of 1198 patients with severe haemophilia A and treated with Advate, Kogenate/Helixate or Refacto AF preswitch were included in the analysis, of whom 516 switched to Refacto‐AF and 682 did not switch products. Five new inhibitors were reported amongst previously treated patients (>50 exposure days) with a median titre at the time of detection of 1.25 BU mL^?1 (IQR 0.7–23.05). One inhibitor occurred in a non‐switcher using Kogenate, an incidence of 1.5 per 1000 treatment‐years (95% CI 0.2–10.5). Four inhibitors arose in patients who had switched from Kogenate (two) or Advate (two) to ReFacto‐AF, an incidence of 7.8 per 1000 treatment‐years (95% CI 2.9–20.8). These incidence rates did not differ significantly from one another (incidence rate ratio 5.3 (95% CI 0.5–260.3) or from the historical rate of 6.05 inhibitors/1000 treatment‐years (95% CI 5.18–7.06). Only one inhibitor (non‐switcher) persisted. Non‐switchers were significantly older (P = 0.03), and used significantly less FVIII per year (P = 0.005) prior to switching. Following switching, factor usage increased similarly (P = 0.53) in both groups. Switching from FLRFVIII to Refacto‐AF (BDDRFVIII) was not associated with an increased inhibitor development.     

Identifying non‐responsive bleeding episodes in patients with haemophilia and inhibitors: a consensus definition

Summary. Assessing response to treatment with bypassing agents presents a substantial challenge in the treatment of patients with haemophilia and inhibitors. Rapid and accurate identification of bleeding episodes that are non‐responsive to bypassing therapy with either Factor Eight Inhibitor Bypassing Activity (FEIBA; Baxter AG) or recombinant activated factor VII (rFVIIa; NovoSeven^®, Novo Nordisk A/S) is essential to guide treatment decisions and optimize patient outcomes through early intervention. Although both bypassing agents are effective, differential responses to therapy necessitate multiple therapeutic options. This article provides a consensus definition for non–life‐threatening joint and muscle bleeds that are non‐responsive to bypassing agents. An international panel of seven physicians met in December 2008 to develop the consensus definition using a modified National Institutes of Health Consensus Development Conference method. The consequent definition of non–life‐threatening bleeding episodes that are non‐responsive to bypassing treatment provides a global picture of the condition of the patient during such an event. Identification of non‐responsiveness is based on various criteria: pain, swelling/tension, mobility, patient perception and laboratory parameters. Criteria can be assessed subjectively by the patient/parent and/or objectively by the clinician. Although the precise timing of each determination should be at the discretion of the physician, bleeds should be considered non‐responsive if the clinical situation meets the specified criteria 24 h from the start of treatment. Although it is not intended to replace clinical judgment, this definition can guide the optimal course of treatment for patients with haemophilia and inhibitors.     

Hydrolysis of factor VIII mediated by catalytic antibodies occurs in haemophilia A patients with or without factor VIII inhibitors

The major complication of the substitutive treatment of haemophilia A (HA) is the development of antifactor VIII (FVIII) antibodies. Most of these antibodies neutralize FVIII procoagulant activity, and are identified as FVIII inhibitor. A subgroup of these antibodies, ‘catalytic antibodies’, catalyses the FVIII hydrolysis. We investigated the frequency and the activity of catalytic antibodies, according to the phenotype of HA and the presence or absence of FVIII inhibitor. IgG from 16 patients with inhibitor and 17 patients without inhibitor were purified. Rates of FVIII hydrolysis and inhibitor titres were evaluated. Anti‐FVIII catalytic antibodies were detected in 63.6% of patients with HA, irrespective of the HA phenotype and the presence of FVIII inhibitor. The frequency was significantly higher for severe HA patients (73.3%) and patients with inhibitor (87.5%), but their FVIII‐proteolytic activity was not significantly different from patients with mild or moderate HA and patients without inhibitor. The evolution of both catalytic and inhibitory activities was studied for 11 patients with FVIII inhibitor. We observed two profiles. In the profile 1, 18.2% of patients, the catalytic activity and the inhibitor titre coevolved. In contrast, a dissociated evolution of these two parameters was observed in 72.8% patients in profile 2. These data confirm the importance of anti‐FVIII catalytic activity in patients with severe, moderate and mild HA. Interestingly, most of the patients presented a dissociated profile, suggesting that anti‐FVIII antibodies might not systematically act as FVIII inhibitors.     

A cross‐sectional study of bleeding phenotype in haemophilia A carriers

Haemophilia A carriers have historically been thought to exhibit normal haemostasis. However, recent data demonstrates that, despite normal factor VIII (FVIII), haemophilia A carriers demonstrate an increased bleeding tendency. We tested the hypothesis that obligate haemophilia carriers exhibit an increase in clinically relevant bleeding. A cross‐sectional study was performed comparing haemophilia A carriers to normal women. Questionnaire assessment included a general bleeding questionnaire, condensed MCMDM‐1VWD bleeding assessment tool and Pictorial Bleeding Assessment Chart (PBAC). Laboratory assessment included complete blood count, prothrombin time, activated partial thromboplastin time, fibrinogen activity, FVIII activity (FVIII:C), von Willebrand factor antigen level, ristocetin cofactor, platelet function analyser‐100^TM and ABO blood type. Forty‐four haemophilia A carriers and 43 controls were included. Demographic features were similar. Laboratory results demonstrated a statistically significant difference only in FVIII:C (82·5 vs. 134%, P < 0·001). Carriers reported a higher number of bleeding events, and both condensed MCMDM‐1 VWD bleeding scores (5 vs. 1, P < 0·001) and PBAC scores (423 vs. 182·5, P = 0·018) were significantly higher in carriers. Haemophilia A carriers exhibit increased bleeding symptoms when compared to normal women. Further studies are necessary to fully understand the bleeding phenotype in this population and optimize clinical management.     

Inhibitor incidence after intensive FVIII replacement for surgery in mild and moderate haemophilia A: a prospective national study in the Netherlands

Inhibitor development is currently the most severe complication in mild/moderate haemophilia A patients, causing increased bleeding tendency, hospitalization and mortality. It has been suggested that receiving high doses of factor VIII (FVIII) concentrates for surgical procedures is an important risk factor for inhibitor development in these patients. The current multicentre study aimed to determine prospectively the incidence of inhibitor development after intensive FVIII replacement therapy for surgical procedures in patients with mild/moderate haemophilia A. All consecutive patients with mild/moderate haemophilia A were included when they required at least 10 000 iu of FVIII concentrates (or 250 iu/kg) for 5 or more days for a surgical procedure. Potential clinical risk factors for inhibitor development and results of inhibitor tests were collected. Forty-six patients with a median age of 54 years (interquartile range, 40-59 years) were included in the study. F8 genotyping revealed 20 different missense mutations. Patients received either recombinant (65%) or plasma-derived FVIII concentrates (35%) by intermittent bolus injections (41%) or continuous infusion (57%). Two patients developed a low titre inhibitor post-operatively. The incidence of inhibitor development following intensive treatment for surgery in this unselected prospective cohort of mild/moderate haemophilia A patients was 4% (95% confidence interval, 0·5-14·8).     

Efficacy of FEIBA for acute bleeding and surgical haemostasis in haemophilia A patients with inhibitors: a multicentre registry in Turkey

Long used in established industrialized nations to treat patients with haemophilia and inhibitors, factor eight inhibitor bypassing activity (FEIBA) has, in recent years, been introduced into more geographically diverse settings. Data are needed on how successfully FEIBA therapy has been implemented in new regions. To determine the efficacy and safety of FEIBA for the treatment of acute bleeding and surgical haemostasis in a newly industrialized country. A multicentre registry of haemophilia A patients with inhibitors receiving FEIBA treatment was established in Turkey. With a standardized case report form, data were collected retrospectively on: patient demographics; characteristics of acute bleeding episodes and surgical interventions; FEIBA regimen; and treatment outcomes. Thirty-seven patients received a total of 112 FEIBA treatment courses, 90 for acute bleeding and 22 for surgical haemostasis. The median FEIBA dose per infusion for acute bleeding was 50 IU kg(-1), and for surgery was 100 IU kg(-1). For both acute joint and muscle/soft tissue bleeding and in surgery, haemostasis was attained in a median of two FEIBA infusions. FEIBA was judged effective in 92% of treatment courses for acute bleeding, with a 95% confidence interval (CI) of 85-97%. Rates of haemostatic efficacy did not differ significantly between anatomical sites of acute bleeding. The haemostatic efficacy rate of FEIBA in surgery was 86% (CI, 65-97%). No thromboembolic complications or other adverse events occurred during any treatment course. FEIBA has been successfully integrated into clinical practice in Turkey, with rates of haemostatic efficacy comparable to those reported in countries with a longer history of FEIBA usage.     

Persistent factor VIII inhibitors and orthopaedic complications in children with severe haemophilia A

Summary. Persistence of inhibitors against factor VIII (FVIII) may be a risk factor that increases physical disability in haemophilia A (HA) patients. This study aimed to evaluate prevalence of FVIII inhibitors in previously treated children with severe HA and the impact of persistent inhibitors on knee joint status and lumbar bone mineral density (BMD). Fifty children with severe HA, FVIII <1%; aged 5–16 years were enrolled in this study; they received plasma‐derived FVIII on‐demand treatment for 50–250 exposure days (EDs). Inhibitors were checked at basal visit and were followed up for 1 year, using Bethesda assay. Cross‐sectional clinical scoring and radiological evaluation of the knee joint (by Arnold‐Hilgartner staging and Pettersson score), along with lumbar BMD by Dual Energy X‐ray Absorptiometry (DEXA) were performed. Patients with persistent inhibitors for 1 to 5 years, median 2.5 years, were 10 (20%). Six had high titre and none of them had completely normal knees, seven had advanced knee arthropathy and six had low lumbar BMD in comparison to 2 and 8 of the 40 patients without inhibitors respectively (P < 0.05). Persistence of inhibitors for more than 2 years without immuno‐prophylaxis was a risk factor for joint damage. Low lumbar BMD was found in 88.9% of patients with stages four and five knee arthropathy and in 66.7% of patients with positive hepatitis C. Severe HA children in this Egyptian study had a relatively low prevalence of persistent FVIII inhibitors, which, if not treated, may increase the risk of knee arthropathy and lumbar osteopenia.